 /*******************************************************************************
  * Copyright (c) 2000, 2005 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.ui.texteditor.templates;

 import java.util.ArrayList ;
 import java.util.Collections ;
 import java.util.Comparator ;
 import java.util.Iterator ;
 import java.util.List ;

 import org.eclipse.jface.text.ITextViewer;
 import org.eclipse.jface.text.contentassist.ICompletionProposal;
 import org.eclipse.jface.text.contentassist.IContentAssistProcessor;
 import org.eclipse.jface.text.contentassist.IContextInformation;
 import org.eclipse.jface.text.contentassist.IContextInformationValidator;
 import org.eclipse.jface.text.templates.TemplateContextType;
 import org.eclipse.jface.text.templates.TemplateVariableResolver;



 /**
  * A content assist processor for template variables.
  * <p>
  * This class should not be used by clients and may become package visible in
  * the future.
  * </p>
  *
  * @since 3.0
  */
 final class TemplateVariableProcessor implements IContentAssistProcessor {

     private static Comparator fgTemplateVariableProposalComparator= new Comparator () {
         public int compare(Object arg0, Object arg1) {
             TemplateVariableProposal proposal0= (TemplateVariableProposal) arg0;
             TemplateVariableProposal proposal1= (TemplateVariableProposal) arg1;

             return proposal0.getDisplayString().compareTo(proposal1.getDisplayString());
         }

         /*
          * @see java.lang.Object#equals(java.lang.Object)
          */
         public boolean equals(Object arg0) {
             return false;
         }

         /*
          * Returns Object#hashCode.
          * @see java.lang.Object#hashCode()
          */
         public int hashCode() {
             return super.hashCode();
         }
     };


     /** the context type */
     private TemplateContextType fContextType;

     /**
      * Sets the context type.
      *
      * @param contextType the context type for this processor
      */
     public void setContextType(TemplateContextType contextType) {
         fContextType= contextType;
     }

     /**
      * Returns the context type.
      *
      * @return the context type
      */
     public TemplateContextType getContextType() {
         return fContextType;
     }

     /*
      * @see IContentAssistProcessor#computeCompletionProposals(ITextViewer, int)
      */
     public ICompletionProposal[] computeCompletionProposals(ITextViewer viewer, int documentOffset) {

         if (fContextType == null)
             return null;

         List proposals= new ArrayList ();

         String text= viewer.getDocument().get();
         int start= getStart(text, documentOffset);
         int end= documentOffset;

         String string= text.substring(start, end);
         String prefix= (string.length() >= 2)
             ? string.substring(2)
             : null;

         int offset= start;
         int length= end - start;

         for (Iterator iterator= fContextType.resolvers(); iterator.hasNext(); ) {
             TemplateVariableResolver variable= (TemplateVariableResolver) iterator.next();

             if (prefix == null || variable.getType().startsWith(prefix))
                 proposals.add(new TemplateVariableProposal(variable, offset, length, viewer));
         }

         Collections.sort(proposals, fgTemplateVariableProposalComparator);
         return (ICompletionProposal[]) proposals.toArray(new ICompletionProposal[proposals.size()]);
     }

     /* Guesses the start position of the completion */
     private int getStart(String string, int end) {
         int start= end;

         if (start >= 1 && string.charAt(start - 1) == '$')
             return start - 1;

         while ((start != 0) && Character.isUnicodeIdentifierPart(string.charAt(start - 1)))
             start--;

         if (start >= 2 && string.charAt(start - 1) == '{' && string.charAt(start - 2) == '$')
             return start - 2;

         return end;
     }

     /*
      * @see IContentAssistProcessor#computeContextInformation(ITextViewer, int)
      */
     public IContextInformation[] computeContextInformation(ITextViewer viewer, int documentOffset) {
         return null;
     }

     /*
      * @see IContentAssistProcessor#getCompletionProposalAutoActivationCharacters()
      */
     public char[] getCompletionProposalAutoActivationCharacters() {
         return new char[] {'$'};
     }

     /*
      * @see IContentAssistProcessor#getContextInformationAutoActivationCharacters()
      */
     public char[] getContextInformationAutoActivationCharacters() {
         return null;
     }

     /*
      * @see IContentAssistProcessor#getErrorMessage()
      */
     public String getErrorMessage() {
         return null;
     }

     /*
      * @see IContentAssistProcessor#getContextInformationValidator()
      */
     public IContextInformationValidator getContextInformationValidator() {
         return null;
     }

 }


